42.
EDIT: Ninja'd. Knew someone else would post that.
OT: To be honest with you, none of us can give you the meaning to life, because its a very personal sort of thing. Ultimately, it comes down to living your life, setting goals for yourself, and doing all you can to achieve those goals, no matter how trivial. Now, some of us, like me, find that religion helps. In my case, being a Christian, the meaning to life is figuring out Gods will and following it.
Now, before anyone flames this post, don't get me wrong, I'm not promoting my religion or bashing others. You believe what you believe, and in all honesty, people tend to need to believe in SOMETHING, even if its something simple. And I'm not saying people NEED religion specifically. What you believe is your business, and its no business of mine to judge you for it. But, religion CAN give some of us a guiding hand to help us find meaning in our lives. Others find that personal goals are enough. Whatever gives you meaning, hold onto it. Even if it happens to be love for another person.
I think we can all say that we've either thought about this very question at least once, or have either felt sure enough or not cared enough to not think about it.
Whatever the case, meaning or not, life is worth living, and you are the one who ultimately steers your life. Sure, there is plenty of outside influence, but its YOU who decides whether to stand there and let life take you where it wills, or to drive forward on your own. We can't give you the answers, and not just because a lot of us don't have the answers ourselves.
You're the only one who can find meaning in your own life.